Electric-resistance element



Jan. 19', 1926.

. T. C. RUSSELL ELECTRIC RESISTKNCE ELEMENT Filed Feb. 7, 1924 nwllmm ymw Patented Jan. 19, 1926.-

UNITED STATES THOMASC. RUSSELL, 0F CHICAGO, ILLINOIS.

ELECTRIC-RESISTANCE ELEMENT.

Application led February 7, 1924. Serial No. 691,087.

To all whom it may concern:

Be it known that I, THOMAS C. RUSSELL, a citizen of the United States, and a resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Electric-Resistance Elements, of which the following is a speelfication.

My invention relates to electrical resistance elements for use in electric heat devices. In electric heat devices for ordinary heating purposes the resistance or heat element is usually in the form of metallic wire or ribbon of'resistance metal or composition such as nickel chromium. The heat limit of these elements is somewhere in theneighborhood of 1800 degrees Fahrenheit. yIn'some electhat combinations of carbon, carborundum,

and similar non-metallic materials with suitable binders and when moulded or compressed into proper form, such as rods, bars, etc., alord an electrical conductor of high resistance which will have a very long life under practically continuous operation at temperatures as high as 2400 degrees Fahrenheit.

Owing to the high heat developed by the elements under current flow the great problem has been to provide suitable terminals for the conduction of electric current to and from the element. If the terminals doA not have extended and good contact with the elements and are not kept comparatively cool, excessive corrosion, oxidation and burning will soon result and the terminals will be rendered useless or destroyed. Attempts have been made to overcome this difficulty by treating kthe endso the resistance element so as to increase the conductivity and prevent excessive heat from being developed at these points, but the processes so far developed are very expensive and slow. Sometimes the ends after being treated are coated with aluminum paint or some other metallic conductor, but owing to the low melting point and other reasons this procedure has not been satis-l factory and arcing and terminal troubles soon develop.

The object of my invention is to produce terminals for such non-metallic resistance elements which will stand up undei high temperatures and will resist corrosion or oxidation and will always insure good electrlcal connection with the element. This I accomplish by plating the terminal ends of the resistance element with metal such as nickel, chromium, cobalt, or other suitable metal which has comparatively good electrical conductivity and which will withstand the high temperatures to which they will be sub3ected. Such plating is accomplished electrolytically which will insure intimate and extended engagement of the metal with the material of the resistance element. After plating the terminal ends of the element, terminal caps of heat resistance material such as Monel metal are then intimately applied to the plated ends to which caps the current leads can be readily secured. Preferably the ends of the resistance element are threaded so that the ca s can be securely screwed thereto. The plilting metal, being of much higher electrical conductivity than the material of the resistance element, will relieve the resistance element of `sufiicient current flow at its terminal ends to reduce the heat and keep the terminals sutiiciently cool, the platingextending a greater or less distance beyond the ends of the terminal caps depending upon how far it is necessary to keep the heat away from the terminals.

In order to illustrate my invention the accompanying drawing shows it applied to the heating unit for the reflector type electric space heaters. On the drawing I ig. 1 is an elevational view of the heater um Fig 2 is a vertical diametral sectional view,

Fig. 3 is a sectional view on plane 3 3, Fig. 1, and

.Fig 4 is a vertical diametral sectional view of the lower end of the unit, showing a modified arrangement.

In the structure shown 10 indicates the resistance or heat .producing member. It is formed of a combination of carbon, carborundum or other suitable non-metallic materials which are mixed with a suitable binder and then moulded or compressed into the desired form. The member shown is cylindrical and its ends e and e are threaded. These terminal ends are then plated with metal such as nickel, chromium, cobalt or other Asuitable metal which will withstand high temperatures and which is of comparatively high electrical conductivity. The plating is perferably accomplished electrolytically so that the plating metal will penetrate and be in secure intimate engagement with the terminal ends, and the thickness of the plating will depend upon the service to which the heating element is to be sub]ected. The plated ends e and e receive the terminal caps 11 and 12 which are of some good heat resistant material such as Monel metal. The threading engagement permits such caps to be intimately and securely attached and the extensive area afforded by the threads will insure good electrical connection. As the plating metal is of high electrical conductivity as compared to that of the resistance member 10 it will take the current flow away from the resistance member at its terminal ends and will thus reduce the generation of heat at such ends sufficiently to keep the ends and the terminal caps cool and thus prevent oxidation, corrosion or burning. The plating areas p can be extended inwardly of the cap to a greater or less degree depending upon service conditions andso serve to rapidly reduce the heat generation adjacent the terminal caps.

As the terminal caps are kept cool current supply conductors can be readily electrically engaged therewith by ordinary terminal screws or other fittings. In the arrangement shown the heating unit is adapted for insertion into the ordinary terminal socket. A socket engaging screw shell 13 is secured to a body 14 of porcelain or other suitable insulating material, and this body has the passageway 15 for receiving the terminal screw 16 which threads into the terminal cap 11 of the heating element. In Fig. 2 I have shown washers or a sleeve 17 of porcelain or other insulating material interposed between the body 14 and the terminal cap 11 and this leaves an insulating air space 18 between the end of the heating element and the screw shell'. In the modified arrangement of Fig. 4 the body 19 has the neck or sleeve 2O integral therewith instead of separate washers or sleeves.

Extending upwardly from the shell and spaced away from the heating member 10 are one or more rods 21 also preferably of heat resistant material such as Monel metal, 'and these rods are rigidly secured at their upper ends to the terminal cap 12. I preferably employ a number of such rods, four being shown in Fig. 3, the rods then, besides electrically connecting the terminal caps 12 with the screw shell, forming a protecting cage around the heating member. A rigid structure is thus formed which can be readily screwed into an ordinary socket, the screw shell and terminal 16 engaging respectively with the sleeve and tip contacts of the socket. The engagement of the terminal screw 16 with the terminal cap 11 and the engagement of the stiff rod 21 with the terminal 12 keep t,he heating element properly spaced away from the screw shell and the rod. On account of my improved application of the terminal caps to the heating member, and the insulating air space between the cap 11 and the screw shell, this shell and the receiving terminal socket will not become unduly heated. The resistance member 10 between the plating areas will however become highly heated and give eflicient service.

I do not desire to be limited to the exact construction and arrangement shown and described as modifications are possible which would still come within the scope of the invention.

I claim as follows:

1. In an electrical heating unit, the combination of a rigid rod of non-metallic electrical resistance material having its terminal ends electro-plated with high temperature resistant metal, terminal caps secured to said plated ends, a connecting plu structure comprising a body of insulating material, 'a center terminal engaging with one of said caps to secure said rod at one end to said body, a sleeve terminal secured to said body, and bars extending from said sleeve terminal to the other terminal cap, said bars electrically connecting said other cap with said sleeve terminal and also assisting in supporting said rod.

2. In an electrical heating unit, the combination of a rigid rod of non-metallic electrical resistance material having threaded ends, said ends being electro-plated with high temperature resistant metal, terminal caps intimately receiving said threaded ends, and a connecting plug structure comprising a body of insulating material, a center contact extending through said body and threading into one of said terminal caps to secure the rod to said body, a sleeve contact secured to said body, and bars extending from said sleeve to the other terminal cap, said bars electrically connecting said o sleeve terminal with said other ca and serving also to support said rod in alignment.

3. In an electrical hcatin bination with a resistance e ement comprising a resistance member in the form of a c lindrical rod of non-metallic electrical resistance material, said rod having threaded ends and said ends being electro-plated with high temperature resistant metal, and terminal caps secured to such threaded ends, of a circuit connecting plug structure comprising a body of insulating material, a center contact screw extending through said body and engaging with one of said terminal caps to secure one end of said resistance element, a threaded sleeve contact secured to said body, and bars extending from saidL sleeve to the other terminal cap, said bars being spaced away from said resistance element and serving to connect said sleeve with unit, the comv 5 terminal secured to said base, a tip terminal extending through said base concentric with said screw shell terminal, a supporting con* tact cup secured by said tip terminal against the inner side of said base, a resistance mem 10 berseated at one end on said cup and eX- tending therefrom in axial alignment with said hase, a terminai cap for the outer end. of said resistance member, and nare extendw ing from Saidcap to said screw shell terminai Aier supporting the outer end 0f Said sistance member and for connecting` `he out er end thereof electrically with said screw sheii termina,

n Witness whereof, ii hereunto subscribe my name this ist day of February A.,

lra

THSAS C. RUSSELL. 

